The present invention relates to a plastic fan which has several fins attached to a hub. The fins are formed in a mold by plastic injection so as to reduce the difference between them to a minimum.
Conventionally, each plastic fan is an integral unit which has several fins radially projecting from a hub. Such a plastic fan is formed in a mold which has a central portion wherein the hub is molded and several peripheral portions wherein the fins are formed. The fins so produced have a considerable difference between themselves. A fan so produced will not be balanced during rotation, thus causing vibration and noise. Moreover, the mold is disposed in a way that the hub of the mold is disposed horizontally, i.e., some peripheral portions of the mold are retained on a level higher than the remaining peripheral portions of the mold. The fins which are formed in the lower peripheral portions of the mold weigh more than the fins which are formed in the higher peripheral portions of the mold. The fan so produced will not be balanced during rotation, thus causing vibration and noise.